1. Field of the Invention
The invention relates to the production of textured surfaces for medical and industrial applications and is directed more particularly to the production of undercut micro recesses in a surface, a surgical implant made thereby, and a method for fixing an implant to bone.
2. Description of the Prior Art
It is known to use textured surfaces on surgical implants for the purpose of encouraging bone adhesion and thus stabilize the location of the implant relative to the bone. For example, in an artificial hip, consisting of a femoral sub-assembly for positioning in a patient""s femur, and an acetabular sub-assembly for positioning in the patient""s acetabulum, the femoral sub-assembly includes an artificial stem which is typically provided with a textured surface, and the acetabular sub-assembly includes an acetabular cup which is typically provided with a textured surface, the textured surfaces being provided to promote bone in-growth.
The desirability of roughened, textured, bone-engaging surfaces to assure stable positioning of surgical implants has been recognized in U.S. Pat. No. 5,298,115, issued Mar. 29, 1994, in the name of Ian Leonard, U.S. Pat. No. 5,456,723, issued Oct. 10, 1995, in the name of Samuel G. Steinemann, U.S. Pat. No, 5,603,338, issued Feb. 18, 1997, in the name of Keith D. Beaty, U.S. Pat. No. 5,853,561, issued Dec. 29, 1998, in the name of Bruce A. Banks, and U.S. Pat. No. 5,965,006, issued Oct. 12, 1999, in the names of Roland Baege et al.
To produce such textured surfaces, one known method is to provide a mass of titanium spheres vacuum fused onto the datum surface of the implant. This method is described in U.S. Pat. No. 4,834,756, issued May 30, 1989, to Robert V. Kenna. In a similar procedure, described in U.S. Pat. No. 4,644,942, issued Feb. 24, 1987 to Kenneth R. Sump, an extractable component and titanium spheres are densified as a coating, which is fused onto a datum surface of the implant, and the extractable component subsequently is extracted. While an improvement over untreated metal, questions have arisen over the longevity of usefulness of the implanted devices utilizing such surfaces. It is questionable whether there is substantial genuine adhesion. It is believed that the voids formed by the spheres are not sufficient for long-term nourishment of ingrowing tissue and/or bone. Further, there have been failures of prosthetics treated in this manner because of the fusing process adversely affecting metallurgical properties of the implant material, and because of difficulties in removing manufacturing contaminants, such as cutting oils, from the fused sphere network. Still further, the original datum surface, which can be accurately determined, is lost by the application of the coating spheres.
The formation of perforated thin metallic sheets or plates by means of chemical milling and/or photo-chemical etching techniques has been described in U.S. Pat. No. 3,359,192, issued Dec. 19, 1967, in the names of Hans-Joachim Heinrich et al, U.S. Pat. No. 5,606,589, issued Feb. 25, 1997, in the names of Anthony J. Pellegrino et al, and U.S. Pat. No, 5,814,235, issued Sep. 29, 1998, in the names of Anthony J. Pellegrino et al. The processes therein described have been found lacking in precise control over the degree and extent of roughness or texturing.
In U.S. Pat. No. 5,258,098, issued Nov. 2, 1993, to Donald J. Wagner et al, U.S. Pat. No. 5,507,815, issued Apr. 16, 1996, to Donald J. Wagner et al, and U.S. Pat. No. 6,193,762, issued Feb. 27, 2001, in the names of Donald J. Wagner, et al, there are described chemical and electrochemical etching processes used in conjunction with random sprayed patterns of maskant to create a pattern of dots resistant to etching. After etching and maskant stripping repeatedly, a complex pattern is produced. While complex in appearance, such patterns offer little predictability and repeatability between implants, and lack engineered datum points.
Accordingly, there remains a need for a method for producing an engineered textured surface for interlocking with an adjacent body, such as a bone or other ingrowing body.
An object of the invention is, therefore, to provide a method for producing a textured surface which is adapted to interlock with an adjacent body.
A further object is to provide a method for producing undercut micro recesses in a surface of a body.
A still further object is to provide a method for producing such recesses in a desired pattern which is measurable and predictable, and which can be duplicated and repeated precisely in any selected number of surfaces.
A still further object is to provide a method for producing a surgical implant device wherein the material of the device retains its metallurgical properties throughout production.
A still further object is to provide a method for producing textured surfaces for surgical implants, which surfaces promote the ingrowth of tissue and/or bone to securely interconnect the implant and the tissue and/or bone.
A still further object is to provide a method for producing such surfaces which include undercut and interconnecting recesses which promote and facilitate ingrowth of bone and which, upon implantation, facilitate a xe2x80x9cscratch fitxe2x80x9d with bone, to stabilize the position of the surface on the bone and to initiate an interconnection process between the implant and the bone. The xe2x80x9cscratch fitxe2x80x9d is accomplished by the textured surface scraping bone from the implant site during a press fit implantation, thereby producing autografted bone in the voids of the textured surface.
A still further object of the invention is to provide methods for attaching a surgical implant to bone.
A still further object of the invention is to provide a method for bone harvesting and seeding of a surgical implant with particulate bone matter during attachment of the implant to the bone.
A still further object is to provide a method for making a surgical implant which exhibits a precise fit with a bone implant site, to reduce micro-motion between the implant and the bone site.
A still further object of the invention is to provide a surgical implant having undercut micro recesses with sharply defined edges in a bone-engaging surface thereof.
With the above and other objects in view, a feature of the invention is the provision of a method for producing a multiplicity of undercut micro recesses in a surface of an article, such that the article thereby exhibits a greater fractal area at a level below the surface than is exhibited at the surface, the method comprising the steps of applying a maskant layer to substantially an entirety of the article surface, removing the maskant layer in selected loci to expose underlying portions of the article surface in a selected, predictable, and reproducible pattern, applying an etchant to the exposed underlying surface portions for a time sufficient to etch the exposed surface portions and to enable the etchant to etch beneath remaining portions of the maskant layer and produce a multiplicity of undercut recesses, and removing the remaining maskant layer portions to provide the article surface in exposed condition with the multiplicity of recesses undercut and comprising interconnected recesses, to provide an engineered pattern of the recesses.
In accordance with a further feature of the invention, there is provided a method for producing a multiplicity of undercut micro recesses in a surface of an article in a selected pattern which can be repeated in any selected number of surfaces. The method includes the steps of applying a maskant layer to substantially an entirety of a selected surface of the article. The maskant layer is then removed by computer-directed laser ablation in programmed loci to expose underlying portions of the surface of the article in a programmed pattern. An etchant is then applied to the exposed underlying surface portions for a time sufficient to etch the exposed surface portions and to enable the etchant to etch beneath remaining portions of the maskant layer and produce the multiplicity of undercut recesses, and the remaining maskant layer is removed to provide the selected surface in exposed condition with the multiplicity of undercut recesses therein.
In accordance with a further feature of the invention, there is provided a method for producing a surgical implant having facility for stimulating ingrowth of bone upon attachment of the implant to a bone. The method includes the steps of providing a rigid article, applying a maskant layer to substantially an entirety of a datum surface of the article, removing portions of the maskant layer in selected loci to expose underlying portions of the surface of the article, applying an etchant to the exposed underlying surface portions for a time sufficient to etch the exposed surface portions and to enable the etchant to etch beneath remaining portions of the maskant layer and produce a multiplicity of undercut recesses having sharp edges at their intersections with the datum surface, and removing the remaining portions of the maskant layer to provide the datum surface in exposed condition with the sharp edges for shaving particulate matter from the bone, and with the recesses for receiving and retaining the bone particulate matter for stimulating ingrowth of bone.
In accordance with a still further feature of the invention, there is provided a method for producing a textured surface in a surgical implant. The method includes the steps of applying a maskant layer to substantially an entirety of a datum surface of the implant, removing portions of the maskant layer in selected loci to expose underlying portions of the datum surface of the implant, applying an etchant to the exposed underlying datum surface portions for a time sufficient to etch the exposed surface portions and to enable the etchant to etch beneath remaining portions of the maskant layer and produce a multiplicity of undercut recesses having sharp edges at their intersections with the datum surface, and removing the remaining portions of the maskant layer to provide the datum surface in exposed condition with the sharp edges for shaving particulate matter from the bone, and with the recesses for receiving and retaining the bone particulate matter for stimulating ingrowth of bone.
In accordance with a still further feature of the invention, there is provided a method for attaching a surgical implant to a bone, the method comprising the steps of providing a surgical implant having a datum surface, a multiplicity of micro recesses in the datum surface, and bone milling structure on the datum surface, pressing the datum surface against a surface of the bone, and urging the implant along the bone surface to mill particulate bone matter from the bone, wherein the recesses receive and retain the particulate bone matter to stimulate ingrowth of the bone.
In accordance with a still further feature of the invention, there is provided a method for attaching a surgical implant to a bone, the method comprising the steps of providing a surgical implant having a datum surface and a multiplicity of undercut microrecesses in the datum surface, such that the implant exhibits a greater fractal area at the level below the datum surface than is exhibited at the datum surface, intersections of the datum surface and the recesses defining sharp edges, pressing the datum surface against a surface of the bone, and urging the implant along the bone surface, to cause the sharp edges to shave particulate bone matter from the bone, wherein the recesses receive and retain the particulate bone matter to stimulate ingrowth of the bone.
In accordance with a still further feature of the invention, there is provided a method for bone harvesting and seeding of a surgical implant with particulate bone matter during attachment of the implant to the bone, the method comprising the steps of providing a surgical implant having a surface for engagement with a bone surface, the implant having a multiplicity of undercut micro recesses and bone milling structure in the surface thereof, and moving the implant along the bone, such that the milling structure dislocates particulate bone matter from the bone, the bone matter falling into the micro recesses and retained thereby to stimulate ingrowth of the bone into the undercut recesses.
In accordance with a still further feature of the invention, there is provided a method for making a surgical implant having generally opposed datum surfaces spaced from each other by a predetermined distance, each of the datum surfaces being adapted to interlock with a bone surface, the method comprises the steps of providing an article having first and second datum surface portions adapted to respectively engage first and second bone surfaces, the datum surface portions being spaced from each other by the predetermined distance which is substantially equal to a distance between the first and second bone surfaces, applying a maskant layer to substantially an entirety of each of the datum surfaces, removing the maskant layers in selected loci to expose underlying portions of the datum surfaces in a selected pattern, applying an etchant to the exposed underlying datum surface portions for a time sufficient to etch the exposed portions of the datum surfaces and to enable the etchant to etch beneath the remaining maskant layers and produce undercut recesses, and removing the remaining maskant to provide the opposed datum surfaces in exposed condition with the multiplicity of undercut recesses and devoid of structure protruding therefrom.
In accordance with a still further feature of the invention, there is provided a surgical implant comprising an article having a datum surface for abutting engagement with a bone, and a multiplicity of undercut micro recesses in the datum surface, such that the body exhibits a greater fractal area at a level below the surface than is exhibited at the surface. Intersections of the recesses and the datum surface define sharp edges adapted to cut the bone and produce bone particulates. The recesses are adapted to receive and retain the bone particulates cut from the bone by the edges, to stimulate ingrowth of the bone into the recesses.
The above and other features of the invention, including various novel details of components and method steps, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular methods and devices embodying the invention are shown and described by way of illustration only and not as limitations of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.